Reza Naderloo

Understanding population dynamics requires knowledge of reproductive aspects such as sexual maturity, fertility, and growth changes of body components. We analyzed the relative growth and morphometry in a native brachyuran crab, Leptochryseus kuwaitense (Jones & Clayton, 1983), that dominates mud flats along the Iranian coast of the Persian Gulf and Gulf of Oman. The carapace (length, width, height, front), pleon (abdomen) (length and width of the first, third, fifth, and sixth segments), second, third, and fourth walking legs (total length, length, and width of the merus), cheliped propodus (length and width), and eye dimentions (distance between the two eyes and eye-stalk length), and total weight were recorded for 83 specimens. A regression model with a segmented relationship was employed to examine the relative growth patterns of the characteristics in question. The breakpoints identified in the analysis provided insights into the body size at which crabs attain sexual maturity. The carapace length of sexual morphometric maturity in males and females was 20.43 mm and 19.20 mm, respectively. Males exhibited a positive allometric growth for most traits, with adults having a greater slope than juveniles with the exception of body height, weight, and in some traits (e.g., cheliped length and width) this slope is more than double. By contrast, the growth equation for females is positive allometric for the majority of traits in juveniles, whereas were negative allometric in mature individuals. Juvenile individuals of both sexes exhibited morphological similarities, but females tended to have a smaller body size compared to males. The carapace length of the largest male was 24.2 mm (with mean of 21.71 mm, N = 43), 21.7 and (with mean of 20.14 mm, N = 40) for females, a characteristic that is likely associated with their reproductive biology. Because males are larger in body size, energy investment in the growth of walking legs and chelipeds may be crucial for mating and intreasexual cambating. The rate of growth thus exhibited a more rapid increase in males. Our results indicate that the chelipeds do not play a role in combat, but the coloration of the male cheliped plays a role in its selection by females.

Palapedia schubarti n. sp. is the third species of the genus Palapedia, described from the northwestern Indian Ocean. Two species, P. persica and P. apeli, had already been recorded from the Persian Gulf, and the new species is described from farther south in Socotra Island. Palapedia persica has appendages markedly ornamented with large denticles, while P. apeli has distinctly smooth appendages. Compared to the two above-mentioned species, the new species has an intermediate position regarding the spination, with small denticles on the upper margin of the palm, fingers and anterior margin of walking legs. The morphology of the first male gonopod of P. schubarti n. sp. is very close to P. rastripes, described from Ceylon, and P. truncatifrons described from Japan. The new species, however, is easily distinguishable from those two congeners in having a spade form ending and several other characteristics of chelipeds and carapace.

This taxonomic study describes Liomera schubarti n. sp., a newly discovered xanthid crab inhabiting live coral in the Persian Gulf. The new species shares a general resemblance with four other species of this genus, L. bella, L. margaritata, L. rugata and L. yaldwyni, particularly in carapace morphology, but it can be distinguished by the fusion of carapace areolets, specific pattern of granules on the outer surface of the chela and the unique structure of the male first gonopod. This contribution enriches our understanding of the xanthid crab diversity in the Persian Gulf.

This study reports the first record of two brachyuran crab species, Austruca albimana Kossmann, [21] and Tirmilyra concinnus Ghani and Tirmizi [18], from the western Indian coast. Their identification, taxonomic observations, and geographic distribution are provided. The species belong to the families Ocypodidae and Leucosiidae, respectively. This is the first report from Indian waters, as the species are so far reported from Oman, Iran and Persian Gulf. These records emphasize the need for research and conservation efforts in the region to explore the diversity and distribution of brachyuran crabs in Indian waters.

The current patterns of biodiversity have significantly been affected by glacial-interglacial cycles during the Pleistocene period. True freshwater crabs are considered as poor dispersers and terrestrial barriers restrict gene flow between their local populations. Recent studies, however, suggest that certain environmental conditions, such as periods of heavy rainfall and humidity, can facilitate their between-drainage dispersal and will result in the evolution of homogenous genetic patterns among different drainage systems. Here we tested this hypothesis by comparing populations of the endemic freshwater crab Potamon elbursi Pretzmann, 1962 distributed in two drainage systems, the Caspian Sea and Namak Lake, in northern Iran. Our results based on the genetic analysis of 70 new and 61 previously published sequences of the mitochondrial cytochrome oxidase subunit I gene revealed a substantial haplotype diversity in some populations and high levels of local population structuring in others. Initially, we found mixed evidence of genetic differentiation and connectivity among drainages and populations. Genetic differentiation between the two drainages only became apparent after the Sepirdood population (which belongs to the Caspian Sea drainage) was excluded. Subsequently, the two drainages showed significant genetic distinctions, with a limited gene flow between them. Our demographic analyses supported recent population bottlenecks, followed by a rapid demographic and/or spatial expansion dating back to the Pleistocene climatic fluctuations. Species distribution modelling suggests that precipitation during warm weather conditions profoundly affects the distribution of P. elbursi. This study indicates that freshwater crabs can override short land barriers under favorable weather conditions and will have conservation implications in the face of contemporary climatic fluctuations.

The Zagros Mountains, characterized by complex topography and three large drainage systems, harbor the endemic freshwater crab Potamon persicum in Iran. Our study delves into the evolutionary history of P. persicum, utilizing two mitochondrial and one nuclear marker. We collected 214 specimens from 24 localities, identifying 21 haplotypes grouped into two major evolutionary lineages. Substantial differentiation exists between drainage systems and lineages. Historical demographic analysis revealed a significant decrease in population size during the late-Holocene, accompanied by a recent population bottleneck. Species distribution modelling has revealed eastward shifts in suitable habitats between the last glacial maximum and the present day. Following the last glacial maximum, habitat fragmentation occurred, resulting in the establishment of small populations. These smaller populations are more vulnerable to climatic and geological events, thereby limiting gene flow and accelerating genetic differentiation within species. Historical biogeographic analysis traced the origin of P. persicum to the western Zagros Mountains, with major genetic divergence occurring during the Pleistocene. Our genetic analyses suggest that P. persicum may have shown a genetic pattern similar to a classical ring species before the Pleistocene. The Namak Lake sub-basin could have served as a contact zone where populations did not interbreed but were connected through gene flow in a geographic ring. Currently genetic separation is evident between basins, indicating that P. persicum in the Zagros Mountains is not a contemporary ring species. Also, our biogeographical analysis estimated that range evolution may have been driven initially by dispersal, and only during the late Pleistocene by vicariance.